\section{Observation}\label{Sec. Observation}
    The $J=1 \rightarrow 0 $ \  \coa, \cob and \coc lines were observed using 13.7 m telescope of Qinghai Station of Purple Mountain Observatory, from January to May, 2011.

    The half-power beam size is 56\arcsec$\times$ 55\arcsec (at 92.8 GHz).The main beam efficiency is ~50\%, The pointing accuracy is better than 4''.
    A new SIS receiver with nine beam array was employed as the front end. The \coaa line was observed at upper band and \cobb and \cocc were both observed at lower side band. The typical system temperature is 110 K (varies $\sim$ 10$\%$ each beam).
    FFTS spectrometers, with a total bandwidth of 1 GHz and 16384 channels, were used as the back end.  Velocity resolution for \coaa line is 0.16 km/s, for \cobb and \cocc lines is 0.17 km/s.

    The On-The-Fly(OTF) observing mode was employed. Centered at Planck cold cores, 22\arcmin $\times$ 22\arcmin regions were continuously scanned with scan speed of 20\arcsec $\rm\ s^{-1}$ . The rms noise level in T$^*_A$ was 0.2 K for \coaa, and 0.1 K for \cocc. Considering the edges of the maps are rather noisy, only the central 14\arcmin \multi 14 \arcmin areas were taken into account. Utilizing the IRAM software package GILDAS (Guilloteau \& Lucas 2000), OTF data were converted to 3-D cube data with a grid spacing of 30" . For further analysis, we also used MIRIAD (Sault et al. 1995). 